First‐Row Transition‐Metal–Diborane and –Borylene Complexes

Abstract

A combined experimental and quantum chemical study of Group 7 borane, trimetallic triply bridged borylene and boride complexes has been undertaken. Treatment of [{Cp*CoCl}2 ] (Cp*=1,2,3,4,5-pentamethylcyclopentadienyl) with LiBH4 ⋅thf at -78 °C, followed by room-temperature reaction with three equivalents of [Mn2 (CO)10 ] yielded a manganese hexahydridodiborate compound [{(OC)4 Mn}(η(6) -B2 H6 ){Mn(CO)3 }2 (μ-H)] (1) and a triply bridged borylene complex [(μ3 -BH)(Cp*Co)2 (μ-CO)(μ-H)2 MnH(CO)3 ] (2). In a similar fashion, [Re2 (CO)10 ] generated [(μ3 -BH)(Cp*Co)2 (μ-CO)(μ-H)2 ReH(CO)3 ] (3) and [(μ3 -BH)(Cp*Co)2 (μ-CO)2 (μ-H)Co(CO)3 ] (4) in modest yields. In contrast, [Ru3 (CO)12 ] under similar reaction conditions yielded a heterometallic semi-interstitial boride cluster [(Cp*Co)(μ-H)3 Ru3 (CO)9 B] (5). The solid-state X-ray structure of compound 1 shows a significantly shorter boron-boron bond length. The detailed spectroscopic data of 1 and the unusual structural and bonding features have been described. All the complexes have been characterized by using (1) H, (11) B, (13) C NMR spectroscopy, mass spectrometry, and X-ray diffraction analysis. The DFT computations were used to shed light on the bonding and electronic structures of these new compounds. The study reveals a dominant B-H-Mn, a weak B-B-Mn interaction, and an enhanced B-B bonding in 1.

Stabilization of Classical [B2H5]−: Structure and Bonding of [(Cp*Ta)2(B2H5)(μ‐H)L2] (Cp*=η5‐C5Me5; L=SCH2S)

“…The solid‐state X‐ray structure of 1 distinctly shows the bridging of diborane(5) species, positioned unsymmetrically between two tantalum atoms (Figure ). Although the observed B−B distance of 1.74(2) Å is in the range estimated for a directly bonded {H 2 B‐BH 3 } − unit, this is considerably longer as compared to that of [Ta 2 (μ 2 ,η 4 ‐B 2 H 6 )(DTolF) 4 ⋅2 Et 2 O] (1.682 Å) (DTolF= N , N′ ‐di‐ p ‐tolylformamidinate), [Ta 2 (μ 2 ,η 4 ‐B 2 H 6 )(DPhF) 4 ⋅2 Et 2 O] (1.680 Å) (DPhF= N , N ′‐diphenylformamidinate) and [{(OC) 4 Mn}(η 6 ‐B 2 H 6 ){Mn(CO) 3 } 2 (μ‐H)] (1.681(6) Å). Nonetheless, the B1−B2 distance (1.74(2) Å) is equivalent to similar linkages, reported earlier for B(sp 2 )–B(sp 3 ) bonded species, such as [(CuX){(An)B(H)–B(S I Mes)(C 14 H 8 )}] (X=Cl, OTf or Pf; An=9‐anthryl) .…”

Synthesis of Trithia-Borinane Complexes Stabilized in Diruthenium Core: [(Cp*Ru)2(η1-S)(η1-CS){(CH2)2S3BR}] (R = H or SMe)

“…While the Ru-B distances in both 1 and 5 is comparable, the B-B distances show considerable variation. It is worth noting that the B1-B2 bond distance of 1.679(11) Å in 5 is shorter than the normal B-B single bond, but it is comparable to that of a manganese hexahydridodiborate complex [{(OC) 4 Mn}(η 6 -B 2 H 6 ){Mn(CO) 3 } 2 (µ-H)] [39]. The interatomic separation between B3 and S1 (3.029 Å) is significantly longer for the formation of a direct B-S bond, and is bridged via the {S-CH 2 } unit.…”

“…However, there is still little understanding of how a transition metal can be used to vary the chemistry of metallaborane compounds. In this regard, our group was actively involved in the synthesis of various electron-precise transition metal-boron complexes such as σ-borane [26][27][28][29][30][31], boryl [32,33], triply-bridged trimetallic borylene [34][35][36][37][38], diborane [39], B-agostic [26,27,[40][41][42], and metallaboratrane [26,27,43,44] complexes using of different synthetic precursors. An important aspect is the incorporation of transition metals into the chemistry of p-block elements other than carbon [45][46][47].…”

Heterometallic boride clusters: synthesis and characterization of butterfly and square pyramidal boride clusters*

“…Over the past decade, our effort in synthesizing metallaboranes using boranes, metal halides and metal carbonyls allowed us to isolate a variety of boride clusters with varying metal to boron ratio [60][61][62][63][64][65][66][67][68]…”